A typical LCD has the advantages of portability, low power consumption, and low radiation. Therefore the LCD has been widely used in various handheld electronic products, such as mobile phones, notebooks, personal digital assistants (PDAs), video cameras, and the like.
The liquid crystal of an LCD does not itself emit light. Therefore it is common for a light source device to be installed with an LCD to enable the LCD to display images. Typically, the light source device needs a battery for supply of power.
The LCD of a handheld electronic product is typically used in different surroundings and environments. For example, the LCD is sometimes used in high ambient light conditions (e.g., in bright sunlight), and sometimes in relatively low ambient light conditions (e.g., in darkness).
In a typical LCD, the intensity of the light emitted from the light source device is almost constant, therefore the brightness of the LCD is essentially constant. When the LCD is used in high ambient light conditions, the intensity of the ambient light is close to or even higher than that of the light emitted from the LCD. That is, the contrast between the light of the LCD and the light of the environment is low. Therefore a user may not see images on the LCD clearly. When the LCD is used in low ambient light conditions, the intensity of ambient light is much lower than that of the light emitted from the LCD. That is, the contrast between the light of the LCD and the light of the environment is too high. Therefore the images displayed on the LCD may be too bright and displeasing.
Furthermore, the battery installed in the light source device is often quite small and therefore generally only has enough power to keep the LCD running for a few hours. When the LCD is used in low ambient light conditions, the intensity of the light of the LCD is liable to be more than what a user is comfortable with. That is, the power consumption of the LCD is unnecessarily high, and the battery life is needlessly shortened.
What is needed, therefore, is an LCD that can overcome the above-described deficiencies.